CREATE FOREIGN TABLE

Note

Starting with SQream DB v2020.2, external tables have been renamed to foreign tables, and use a more flexible foreign data wrapper concept.

Upgrading to a new version of SQream DB converts existing external tables automatically.

CREATE FOREIGN TABLE creates a new foreign table in an existing database.

See more in the Foreign tables guide.

Tip

  • Data in a foreign table can change if the sources change, and frequent access to remote files may harm performance.
  • To create a regular table, see CREATE TABLE

Permissions

The role must have the CREATE permission at the database level.

Syntax

create_table_statement ::=
    CREATE [ OR REPLACE ] FOREIGN TABLE [schema_name].table_name (
        { column_def [, ...] }
    )
    [ FOREIGN DATA ] WRAPPER fdw_name
    [ OPTIONS ( option_def [, ...  ] ) ]
    ;

schema_name ::= identifier

table_name ::= identifier

fdw_name ::=
    { csv_fdw | orc_fdw | parquet_fdw }

option_def ::=
{
   LOCATION = '{ path_spec }'
   | DELIMITER = '{ field_delimiter }' -- for CSV only
   | RECORD_DELIMITER = '{ record_delimiter }' -- for CSV only
   | AWS_ID '{ AWS ID }'
   | AWS_SECRET '{ AWS SECRET }'
}

path_spec ::= { local filepath | S3 URI | HDFS URI }

field_delimiter ::= delimiter_character

record_delimiter ::= delimiter_character

column_def ::=
    { column_name type_name [ default ] [ column_constraint ] }

column_name ::= identifier

column_constraint ::=
    { NOT NULL | NULL }

default ::=
    DEFAULT default_value
    | IDENTITY [ ( start_with [ , increment_by ] ) ]

Parameters

Parameter Description
OR REPLACE Create a new table, and overwrite any existing table by the same name. Does not return an error if the table already exists. CREATE OR REPLACE does not check the table contents or structure, only the table name.
schema_name The name of the schema in which to create the table.
table_name The name of the table to create, which must be unique inside the schema.
column_def A comma separated list of column definitions. A minimal column definition includes a name identifier and a datatype. Other column constraints and default values can be added optionally.
WRAPPER ... Specifies the format of the source files, such as parquet_fdw, orc_fdw, or csv_fdw.
LOCATION = ... Specifies a path or URI of the source files, such as /path/to/*.parquet.
DELIMITER = ... Specifies the field delimiter for CSV files. Defaults to ,.
RECORD_DELIMITER = ... Specifies the record delimiter for CSV files. Defaults to a newline, \n
AWS_ID, AWS_SECRET Credentials for authenticated S3 access

Examples

A simple table from Tab-delimited file (TSV)

CREATE OR REPLACE FOREIGN TABLE cool_animals
  (id INT NOT NULL, name VARCHAR(30) NOT NULL, weight FLOAT NOT NULL)
WRAPPER csv_fdw
OPTIONS
  ( LOCATION = '/home/rhendricks/cool_animals.csv',
    DELIMITER '\t'
  )
 ;

A table from a directory of Parquet files on HDFS

CREATE FOREIGN TABLE users
  (id INT NOT NULL, name VARCHAR(30) NOT NULL, email VARCHAR(50) NOT NULL)
WRAPPER parquet_fdw
OPTIONS
  (
    LOCATION =  'hdfs://hadoop-nn.piedpiper.com/rhendricks/users/*.parquet'
  );

A table from a bucket of ORC files on S3

CREATE FOREIGN TABLE users
  (id INT NOT NULL, name VARCHAR(30) NOT NULL, email VARCHAR(50) NOT NULL)
WRAPPER orc_fdw
OPTIONS
  (
      LOCATION = 's3://pp-secret-bucket/users/*.orc',
      AWS_ID = 'our_aws_id',
      AWS_SECRET = 'our_aws_secret'
   );

Changing a foreign table to a regular table

Materializes a foreign table into a regular table.

CREATE TABLE real_table
 AS SELECT * FROM some_foreign_table;